1. Field
The invention relates to low-cost three dimensional integrated automotive radars and methods of manufacturing the same. More particularly, the invention relates to a low-cost three dimensional multi-channel automotive radar where each channel can transmit and receive signals.
2. Background
Automotive radar systems are currently being provided in many luxury automobiles. Over the past few years, automotive radar systems have been used with intelligent cruise control systems to sense and adjust the automobile's speed depending on traffic conditions. Today, automotive radar systems are being used with active safety systems to monitor the surroundings of an automobile for collision avoidance. Current automotive radars are divided into long range (for adaptive cruise control and collision warning) and short range (for pre-crash, collision mitigation, parking aid, blind spot detection, etc.). Some automotive radar systems have been developed to operate at 24 GHz and 77 GHz. An example of an automotive radar system is shown in FIG. 1.
FIG. 1 is a cross-sectional view of a prior art radar 100. The radar 100 includes a first Teflon® substrate 101, a second Teflon® substrate 102 and an aluminum plate 103 positioned between the first Teflon® substrate 101 and the second Teflon® substrate 102. Teflon® is a registered trademark of E.I. du Pont de Nemours and Company that is used for polytetrafluoroethylene (PTFE). Therefore, the term Teflon® can be used interchangeably with the term PTFE in this disclosure. A transmit radio frequency integrated circuit (Tx RFIC) 105 and a receive radio frequency integrated circuit (Rx RFIC) 115 are attached to the first Teflon® substrate 101. The radar 100 includes a first low-temperature co-fired ceramic (LTCC) module 125 for the Tx RFIC 105 and a second LTCC module 130 for the Rx RFIC 115. The Tx RFIC 105 and the Rx RFIC 115 are designed for flip-chip mounting to the first Teflon® substrate 101. A separate transmit antenna 110 and a separate receive antenna 120 are attached to the second Teflon® substrate 102 and are connected to the first LTCC module 125 and the second LTCC module 130, respectively, using coaxial transmission lines 135 and 140 and microstrip transmission lines 145 and 150. As shown in FIG. 1, the coaxial transmission lines 135 and 140 pass through the aluminum plate 103.
Prior art radar systems have several drawbacks. For example, prior art radar systems are bulky and expensive, and use a metallic frame for packaging and support. In addition, prior art radar systems, such as the one shown in FIG. 1, require coaxial, microstrip, and waveguide connections between the antennas and the printed circuit board. The large number of connections and transitions (from the Tx/Rx RFIC to a wirebond, to a microstrip, to the waveguide/Coaxial TL, and finally to the antenna) increase the noise and deteriorate the sensitivity and range of the radar system. This is especially critical for the Receiver (Rx) function where the loss of interconnects between the antenna and the Rx RFIC dominate the overall noise figure of the radar 100 and determine its sensitivity.
Therefore, a need exists in the art for low-cost three dimensional integrated automotive radars with minimum number of connections and transitions between the chip and the antenna.